How to get rid of mastitis?

i have a 3 yr old that acidently got up the duff to a p/b keelpie which is a gud thing cause she is 2.. she ended up having 11 puppies not bad for a first little considering the biggest in her blood lines has been 6 unfortunalty she lost one at birth which without being mean i think is a blessing.. all 10 are now 3 weeks old and healthy only problem is on her very end teat it is hugely enlarged i mean like it fills my whole hand what can i do she is in a lot of pain.. help please